resize of memory Dom#0 in ODA VM did not change even after following Doc ID 2154480.1

after  following  Doc ID 2154480.1
we  changed the ODA DOM0 memory  and  rebooted  it

but  change in  value  is  not  showing  up even  after  reboot.
it should be 8GB but  its  still  the  same 4GB

[root@hostname-dom0 ~]# xm list

Name                                        ID   Mem VCPUs      State   Time(s)

Domain-0                                     0  3941    20     r-----   2229.1

oakDom1                                      1 131075    20     -b----   5543.3

[root@hostname-dom0 ~]# grep -i dom0_mem= /boot/grub/grub.conf

#          all kernel /xen.gz dom0_mem=4096M crashkernel=256M@64M extra_guest_irqs=64,2048 nr_irqs=2048

#          kernel /xen.gz dom0_mem=4096M crashkernel=256M@64M extra_guest_irqs=64,2048 nr_irqs=2048

        kernel /xen.gz dom0_mem=8192M crashkernel=256M@64M extra_guest_irqs=64,2048 nr_irqs=2048